Method of classification



Oct. 3, 1939. A, DAMAN 2,174,553

METHOD OF CLAS S IFI CATION Filed Oct. 14, 1935 3 Sheets-Sheet lINVENTOR. ART/fl/f? C. DANA/V 00 q ATTORNEY.

Oct. 3, 1939. c. DAMAN 2,174,553

METHOD OF CLAS S IFI CATION Filed Oct. 14, 1935 3 Sheets-Sheet 2 IINVENTOR. ARTHUR C. DANA/V Oct. 3, 1939. c, D M 2,174,553

METHOD OF CLASSIFICATION Filed Oct. 14, 1955 3 Sheets-Sheet 5 IIIIIII"go k BY ATTORNEY.

Patented Oct. 3, 1939 UNITED STATES 2,174,553 DIETHOD F CLASSIFICATIONArthur C. Daman, Denver, Colo., assignor, by

mesne assignments, to Mining Process and Patent Company, a corporationof Delaware Application October 14, 1935, Serial No. 44,915

25 Claims.

This invention relates to a method of classifying solids in liquidsuspension and relates more particularly to ore-classification in whichslimes in liquid suspension are treated in a primary separation zone andremoved by overflow while coarse material under treatment is conductedto a settling zone through which it descends by gravity and is thereuponsubjected to a dewatering treatment in a second stage of the treatment.

It is an object of the present invention to agitate and aerate thematerial under treatment,

thereby producing buoyant forces which enhance the separation of finesfrom coarse material.

Another object resides in combining in a single treatment, the steps ofclassifying solids in liquid suspension and conditioning the materialfor subsequent treatment.

A further object of the invention is to control the velocities of thematerial at difierent stages 20 in the treatment to thereby promote aclean separation between coarse and fine material.

Still another object of the invention is to provide a primary andsecondary classification in a treatment in which both the primary andthe secondary are subjected to the influence of the same mechanicalagitation.

Other objects reside in the provision of novel steps and treatments aswill more fully appear in the course of the following description.

30 This invention constitutes a continuation-inpart of my co-pendingapplication, Serial No. 581,-

' 129, filed December 15, 1931, for Classifier. Subjects matter commonto both applications have been described and claimed herein in responseto a divisional requirement in said co-pending application.

While the method herein described may be effectively incorporated intovarious types of classification treatments, it has been described and 40illustrated in connection with-the treatment of ore in a finely dividedcondition and in liquid suspension, as a typical application of theinvention.

The ore is prepared for treatment by any well known method, wet-grindingin a ball mill or rod mill being typical. The discharge from the mill isconducted to the classification stage of the treatment. It will beunderstood that the classifying element may be operated in either anopen-circuit or a closed-circuit arrangement. Where .drygrinding isemployed, the ground product must be mixed with a liquid carrier to forma pulp prior to its introduction into the zone of classification.

5,5 The pulp fed to the zone of classification is subjected to bothagitation and aeration in said zone. The agitation intimately intermixesthe air. and pulp, and the fines in the pulp body are acted upon by theminute bubbles of air rising through the liquid body, which elevate thesame 5 to a point of overflow, resulting in a cleaner, more rapidseparation than is obtained by present methods.

The direction and velocity of the moving material is subjected tocertain control influences 10 through the provision of separateagitation and settling zones. Material is moved upwardly through thezone of agitation at a greater velocity than it descends through thesettling zone, and the upward movement is preferably at a progressivelydecreasing velocity in order to promote the settling of oversizematerial.

The settled material is thereafter subjected to a second classificationin the secondary or dewatering stage of the treatment. Fines passinginto this secondary zone with the oversize are separated by aclassifying action and returned to the primary zone of classificationfor further treatment. i

It is advantageous to employ a rotary impeller as the agitating elementof the treatment and to maintain the primary and secondary zones ofclassification in separated and intercommunieating relation. Theimpeller agitates material in the primary zone, and in cooperation withother elements, controls the velocity of material moving upwardly insaid zone and, at the same time, acts as a pump to return the fines fromthe secondary to the primary zone of classification.

From the foregoing description of the treatment, it is clear thatvarious types of apparatus may be effectively employed in practicing theinvention. To promote a better understanding, the invention will behereinafter described in connection with certain apparatus shown and de-40 scribed in my co-pending application, Serial No. 581,129, it beingunderstood that such apparatus, while'efi'ective in performing theprocess, is shown and described merely to constitute an operativearrangement for practicing the invention.

In the drawings in the several views of which like parts have beensimilarly designated:

Figure 1 represents a sectional elevation of an I arrangement ofapparatus, efiective for performing the process;

Figure 2 is a flow sheet, representing the various steps and treatmentsemployed in practicing the process;

Figure 3 is a section taken along the line 3-3,

figure l; Y

modification of the form illustrated in Figure 4;

and

Figure 6, a section taken along the line B-6 in Figure 5.

Referring first to Figure 2, the invention has been described as appliedto closed-circuit classification in conditioning an ore pulp for a frothflotation treatment. It is to be understood that the described treatmentis merely typical of the use of the invention, and that treatments otherthan those illustrated and described may be employed within the spiritand scope of the invention.

Ore and water are first fed into a launder 31 which feeds a mill 40,where the ore is ground to a predetermined degree of fineness, andthereafter is discharged into a classifying element 5. This elementcomprises a primary classification zone A and a secondary classificationor dewatering zone B.

Oversize material of the treatment in the primary zone A is deliveredinto the secondary zone B and moved to an elevated discharge outlet 3|from which it is passed into the launder 31 and returned to the mill forregrinding.

Fines in the secondary zone B are returned to the primary zone A forre-treatment. Reagent is fed into the primary zone A by a suitablefeeder 39, which preferably is the type that automatically feedsmeasured amounts. The pulp and reagent are subjected to the influence ofagitation and aeration in the primary zone A and the slimes passingacross into an overflow launder 4| at the topof the primary zoneconstitute a conditioned pulp which is fed into a series of flotationcells 42 where the values are concentrated and discharged in a froth byoverflow into a launder 43.

Referring now to Figure 1 of the drawings which illustrates a type ofapparatus well adapted for performing the process, the primaryclassifying element A comprises an inverted cone-shaped vessel 5 havinga circular weir 6 for the overflow of slimes, and having at its lowerend, an outlet I for the delivery of coarse settling products of theprimary classifying operation, to the dewatering and conveying elementB.

The weir has a loose rim 8 which may be ad-- justed to raise or lowerthe line of the overflow which determines the liquid level in thevessel. Two concentrictubes 9 and I in the vessel have their common axiscoincident with the vertical axis of the cone-shaped vessel, andconjointly provide an element for conveying material-fed into the spacebetween the tubes through a launder 12, to the lower portion of thevessel.

A rotary movement is imparted to the inner tube by means of a worm wheell3 supported on a bearing l4 above the vessel and the two tubes arerigidly connected by cross-tubes I5 adjacent their upper ends and by anaperturedflange 16 at their lower ends. The outer tube has at its upperend a bell-shaped enlargement I'I into which the material is fed fromthe launder l2 and exteriorly of the rim of this enlargement are twoopposite shields l8 ordirecting upwardly connections l5 at the materialfed into the mouth of the outer tube and air may enter the inner tube,and a sliding valve Zll around the inner tube, normally resting on thecross-connections I5, is adjustable to control the passage of materialthrough the openings l9.

A shaft 2! coaxial with the vessel, extends through the inner tube andcarries at its end below the same, an impeller 22 adapted to impart anupward thrust to the material discharged from the tubes. 7

The impeller is rotated through the medium of a sheave 23 supportedabove the worm-wheel l3. A conical baffle 24, is fastened as by arms 25to rotate with the concentric tubes, and its lower end houses a part ofthe impeller in spaced relation thereto.

Another similar baffle-ring 26 laps at its lower end over the upperportion of the baffle 24 in spaced relation thereto and is heldstationary by connection with the wall of the vessel.

Scrapers 2'! provided with slanting'blades, are connected with therotary parts of the classifier, as by means of arms 28, to compelsettling material to move along the inner surface of the vessel to thedischarge opening 1. The arms 28 of the scrapers may be attached to avertically adjustable ring 35 around the mouth of the feed tube. Byadjustment of this ring the position of the scrapers may be varied, andthe edge of the mouth of the feed tube, if necessary, may be elevated toa plane above the liquid level in the vessel.

To permit the use of the device as a conditioner in addition to itsfunction as a classifying element, a conduit 38 from a reagent feeder 39communicates with the launder 2 for the supply of reagent to the primaryclassifying element.

The element B comprises a tube 29, preferably rigid, and connected withthe outlet 1 of the classifier by a flexible .elbow 30. The tube 29slants upwardly from the opening with its sanddischarging upper end 3|above the plane of the liquid level in the vessel.

When the classifier is operated in closed-circuit,

the end 3| may be connected with suitable conduits (not shown), andwhere necessary, a suitof oversize material to the grinding element maybe employed.

In Figure 2 another arrangement has been illustrated in which thedischarge from tube 29 is fed directly into launder 31.

The foregoing are merely cited as typical, and any arrangement wherebythe material discharged from the tube 29 may be returned to the grindingelecent 40 may be employed within the spirit and scope of the invention.

able pump-element, (not shown) for the return A vibratory, longitudinalmotion is imparted to the tube 29 by means of electrical vibrators 32,in order to convey the sands upwardly through the tube to its dischargeopening. The vibratory movement may be differential to accelerate theupward movement of the sands by alternate slow and rapid strokesimparted to the tube by the vibratory devices. It is apparent that thesedevices may be of any desired character within the scope of theinvention.

The vibratory motion of the tube 29 may be communicated to the vessel 5in order to expedite the separation of the coarse matter from the finesin the material under treatment. The vessel and the tube are supportedfor conjoint vibration in such case. Any suitable structure may beemployed to support the apparatus and inasmuch as such s ructure must bevaried according to the 2,174,558 construction of the mill in which theclassifier is erected, detailed illustration of the same has beenomitted from the drawings.

In order to maintain the material under treatment at the proper densityfor the separation of its fine and coarse constituents in a settlingaction, water may be supplied to the classifier at anydesired point, asfor example, at the bend of the elbow below the discharge opening, asshown at 33.

Water may also be supplied to the conveyor as by means of a tube 34, toaccelerate the upward.

movement of dewatered sands, in case the density of the material in thetube exceeds a predetermined normal. In addition, the water introducedin this manner facilitates classification in the material passingthrough the tube by washing down fines which have been trapped in thecoarse material.

By extending the conveyor above the plane of the liquid level in theclassifier, a hydrostatic balance is established and the coarse mattermoved above said plane by the vibratory movement, is delivered throughthe end of the con.- veyor in a comparatively dry conditionandsubstantially free of fines and 'slimes The oversize discharge fromthe conveyor is conducted to the .The upward thrust imparted to thematerial causes it to move in an upward current through the conicalbaiile 24, and thence through the upper stationary baille 26, asindicated by the arrows.

liquid current to move to the lower part of the settling vessel over theupper edges of the baflles.

The finer matter in suspension is divided into fine slimes which rise tothe liquid level to be discharged across the overflow, and middlingswhich enter the space between the shields l8 and the feed tube Ill andpass through the crossconnections I 5 into the inner tube 9 for re-'classification upon its return into the zone above the impeller. 1

By thus moving a part of the material in a closed circuit, it is cleanlydivided by repeated separative actions into the slimes which pass acrossthe overflow under the buoyant influence of the aeration, and the coarsesands which pass through the outlet 1 of the vessel into the conveyingand dewatering element B, the operation of which has been describedhereinbefore.

The scraping action of the rakes 21 moving over the inner surface of theconical vessel, insures a constant movement of all of the gravitatingsands to and through the outlet.

During the upward movement of. the material under the influence of theagitation and During the upward movement of the material, coarseparticles thereof settle out of the The circulatory movement of the pulpin the classifier aids in maintaining its proper density. Waterintroduced under pressure through the opening 33 aids in producing thesame-result and, moreover, washes the settling sands into the conveyorelement B, and thereby replaces slimes that have moved downwardly withthe'sands, which are subsequently returned to the primary classificationzone by the vibratory motion and by "the suction infiuence of theimpeller.

It will be apparent from the foregoing that material is moved upwardlyin the primary classification zone at greater velocity than it movesdownwardly in the settling zone. The arrangement of the impeller 22,tubes 8 and I0, and

baflles 24 and 28 permits a velocity control which The water supplied tothe conveyor through the pipe 34 also functions to force and washdownwardly the slimes carried upwardly with the sands, for their returnto the primary zone of classification under the suction'infiuence of theimpeller.

Owing to the circulatory movement of the pulp in the classifier, butlittle water is required to maintain the pulp density. The vibratorymovementbf theap'paratus, together with the agitation and aeration keepstheslimes in suspension and thus accelerates their movement to the levelof the liquid in the vessel.

The impeller may function as an aerator by creating a vortex which drawsin atmospheric air through the tubes 9 and I0, and in that ca- I pacityfurther aids the separation of material.

In case it is desired to deliver the feed" and/or reagent into thecentral zone above the impeller, together with the circulating slimes,the openings I9 of the inner tube may be opened by adjustment of thevalve 20,112 which case the discharge openings of the outer tube areplugged asindicated '-in broken lines at'sfi'in Figure 1, and byregulatcharged from the primaryclas'sifier A is effected by means of oneor more reciprocating rakes 44 moving over the .sloping bottom of a tank45, in which the primary settling vessel is disposed.

A suitable mechanism for: longitudinal reciprocation of the rakescombined with alternate upward and downward movements, is'shown at 46.This mechanism is old in the art, andfurther detailed descriptionneed'not be given.

The construction of the primary classifying element A difiers from thatillustrated in Figure 1, mainly'in that the conical vessel-has in theupper portion of its wall, outlets 41 for the return flow of middlingsexteriorly of the vessel to the outlet I at the lower ,end of the same.

A second-smaller impeller connected with the other rotates in the lowerzone of the vessel to effect or accelerate the upward movement of themiddlings through the outlet, together with ny slimes that may have beencarried upwardly with the sands by the rakes ,4. r I

The rakes movebelow the outlet of the classifier and the outlethas'been' slotted as at 48, to

- prevent possible clogging of the sands and facilitate their movementto the conveyor.

The outlet 3 la of the tank, is likewise above the liquid level in thevessel, and the tank has below the primary classifying element A. Theimpeller 22 in this form of the invention projects through the outlet 1of the primary classifier, and the matter passing downwardly across thebaflies, is discharged into the tank 45 of the rakes, to be returned inpart to the classifying vessel by the action of the impeller.

By the provision of openings 50 in the lower conical baillle, throughwhich the coarser particles may settle, one or more of the plurality ofbaffles may be omitted. Otherwise, the primary classifying element issubstantially the same as those hereinbefore described.

The impeller is partially below the rakes in the conveying element B. Itwill be understood that if desired, the impeller may be entirely belowthe rakes, which is of particular value in re-fitting old classifiers ofthe rake type now in use.

From the foregoing, it will be apparent that the feed, air and/orreagent is subjected to the action of the impeller in the primaryclassification zone, and directed in an upwardly direction.

Coarser material is moved outwardly and settles by gravity, while thefines continue to rise and pass across the overflow. The coarserparticles pass into the zone of influence of the conveyor and are movedto an elevated point of discharge in ade-watering treatment.

Fines entrapped wlth'the sands are subjected to additional washing andagitation in the secondary zone B, and are returned to the primary zoneA by the action of the impeller.

The entire apparatus of the forms illustrated in Figures 4 and 5, likethat of Figure 1, may be supported for vibration.

Where the term flotation reagent is used, it is intended to includedispersion agents, which keep the fines dispersed and aid their passageacross the over-flow; or which cause certain fineconstituents of thepulp to form in flocks and settle with the oversize; and, also, agentsthat assist in the attachment of mineral particles to air bubbles in thepulp whereby such particles are elevated to thesurface and pass acrossthe over-flow. 4

Changes and modifications may be availed of within the spirit and scopeof the invention, as defined in the hereunto appended claims. 7

What I claim and desire to secure by Letters Patent is:

1. The method of classifying finely divided solids in liquid suspensionwhich comprises agitating a pulp, continuously introducing air into thezone of agitation to form a mineral bearing froth, directing the finesin the material up-- ,the agitation and aeriation, dischargingsubstantially all liquids, fines, and formed froth together at thesurface into an overflow, whereby said froth and the uplift of materialserve to raise larger particles to said overflow inducing a settling ofcoarse material by moving the same into a relatively quiescent zone outof the zone of agitation, de-watering the settled material by conductingthe same to an elevating discharge and maintaining a hydrostatic balancebetween the agitation and ole-watering zones.

3. The method of classifying finely divided solids in liquid suspensionwhich comprises agitating a pulp, continuously introducing a controlledflow of air into the same under the influence of the agitation to form amineral bearing froth, directing the fines in the material upwardly inthe pulp body under the influence of the agitation and aeration,discharging substantially all liquids, fines and formed froth togetherat the surface into an overflow, whereby said froth and the uplift ofmaterial serve to raise larger particles to said overflow inducing asettling of coarse material by moving the same into a relativelyquiescent zone out of thezone of agitation, and regulating the elevatingeffect of the aeration by varying the quantity of air admitted to theagitation zone.

4. The method of classifying solids in liquid suspension which comprisesagitating a pulp, directing the pulp body in a circulatory movementupwardly through an inner zone, and downwardly through a larger outerzone, under the influence of the agitation, discharging substantiallyall liquid, lines, and formed froth at the surface into an overflow,progressively increasing the area of the stream of material during itselevation through the inner zone, progressively decreasing the velocityof the rising material, and discharging coarse material adjacent a lowermeeting point of said zones.

5. The method of classifying solids in liquid suspension which comprisesagitating a pulp, directing the pulp body in a circulatory movementupwardly through an inner zone, and downwardly through a larger outerzone, under the influence of the agitation, discharging substantiallyall liquid, fines, and formed froth at tht surface, into an overflow,increasing the area of the stream of material during its elevationthrough the inner zone, and decreasing the velocity of the risingmaterial in ratio to its degree of area increase, and discharging coarsematerial adjacent a lower meeting point of said zones. I

6. In a method of classifying solids in liquid suspension, the step ofimparting to a pulp, a circulatory, elevating movement through an innerzone, and a dire ct downward movement through a larger outer zone,discharging substantially all liquid, fines and formed froth at thesurface into an overflow, said downward movement being at a slowervelocity than the upward movement through the inner zone, whereby aSettling action takes place, and discharging coarse material adjacent alower meeting point of said zones.

'7. In a method of classifying solids in liquid suspension, the step ofsimultaneously increasing the area and decreasing the velocity of acirculatory body of pulp being elevated through an inner zone, andmoving downwardly through a larger outer zone, the degree of increasebeing in inverse ratio to the decrease in velocity, dischargingsubstantially all liquids, fines and formed froth at the surface into anoverflow, and discharging coarse material adjacent a lower meeting pointof said zones.

8. The method of classifying solids in liquid suspension which comprisesagitating a pulp,

introducing air into the zone of agitation, imparting a vibratorymovement to the material being treated, directing the fines in thematerial upwardly under the combined influence of the agitation,the'aeration and the vibratory movement, inducing a settling of coarsematerial under the influence of the vibratory movement in a quiescentzone out of the agitation zone, and discharging substantially allliquid, fines and formed froth at the surface into an overflow.

9. The method of classifyingsolids in liquid suspension which comprisesagitating a pulp, introducing air into the zone of agitation, impartinga vibratory movement to the material being treated, directing the finesin the material upwardly under the combined influence of the agitation,the aeration, and the vibratory movement, inducing a settling of coarsematerial under the influence of the vibratory movement in a quiescentzone beyond the agitation zone, and subjecting the settled material to asecond classification under the influence of the vibrator movement.

10. The method of classifying solids in liquid suspension whichcomprises agitating a pulp, continuously introducing air into the zoneof agitation, imparting a movement to the -material being treated, bythe introduction of pressure fluid into the zone of agitation, directingthe material upwardly through aninner zone under the combined influenceof the agitation, the aeration, and the pressure fluid, and downwardlythrough a larger outer zone, and inducing a settling of coarse materialin said outer zone beyond the zone of agitation.

1 The method of classifying solids in liquid suspension which comprisesagitating a pulp, continuously introducing air into the zone ofagitation, imparting a movement to the material being treated, by theintroduction of pressure fluid into the zone of agitation, directing thematerial upwardly through an inner zone under the combined influence ofthe agitation, the aeration and the pressure fluid, and downwardlythrough a larger outer zone, inducing a settling of coarse material insaid outer zone beyond the zone of agitation, de-watering the settledmaterial by conducting the same to an elevated discharge, and subjectingthe said material to the action of a pressure fluid during itselevation.

12. The method of classifying solids in liquid suspension whichcomprises subjecting a pulp to mechanical agitation, directing thematerial upwardly through an inner zone under the influence of theagitation, inducing a settling of coarse material in a larger outer zonebeyond the zone of agitation, subjecting the settled material to asecondary classification in a dewatering zone, and returning fines fromthe secondary classification to the agitation zone under mixing a pulp,air and a flotation reagent in the pumping influence of the mechanicalagitation.

13. The method of classifying finely divided solids in liquidsuspension, which comprises agitating a pulp, aerating the pulp in thezone of agitation to form a mineral bearing froth, directing fines inthe pulp and the froth together upwardly to an overflow, whereby saiduplift of fines and froth serve to raise larger particles .to saidoverflow inducing a settling of coarse material by moving the same intoa quiescent zone beyond the zone of agitation, and controlling thedensity of the settled material by the introduction of a liquid underpressure into the lower portion of the same,

14. The method of classifying solids in liquid suspension, whichcomprises intimately intermixing a pulp, air and a flotation reagent ina classification zone, directing the material in a circulatory movementupwardly through said zone and downwardly through another larger zone,thereby elevating fines including mixed fines and reagent through saidclassification zone, overflowing substantially all the liquid, fines andformed froth together at the surface of the body, and inducing settlingof circulating sands and other 'material not acted on by the reagent inthe larger zone, beyond the influence of the aeration.

15. The method of treating ore which comprises grinding an ore,suspending the ground product in a liquid carrier to form a pulp,intermixing the pulp with flotation reagents in a zone of classificationunder the combined influence of agitation and aeration, to conditionfines in the pulp, overflowing substantially all the liquid, fines andfroth together from the surface of the body, treating fines of theclassification in a froth flotation treatment in the presence of addedreagent, to reject fine gangue, inducing settling of the remainingsolids of the classifi-. cation, and returning same for regrinding.

16. The method of classifying solids in liquid suspension, whichcomprises intimately intermately intermixing the pulp and a flotationreagent in a zone of classification under the combined influence ofagitation and aeration, to condition fines in the pulp, overflowingsubstantially all the liquid, fines in the pulp, and froth together atthe surface of the body, treating fines of the classification in a frothflotation treatment inthe presence of additional flotation reagent toreject fine gangue, inducing settling of ,the' remaining solids of theclassification, and

returning same for regrinding.

8. The method of treating ore which comprises wet grinding an ore toform a pulp, intimately intermixing the pulp and a flotation reagent ina zone of classification under the combined influence of agitation andaeration, to 1 condition fines in the pulp, overflowing substantiallyall the liquid, fines and formed froth together at the surface ofthebody, passing the fines of the classification to a froth flotationtreatment to reject fine gangue, inducing settling of the remainingsolids of the classification, and retuming-same for regrinding.

19. The method of treating ore, which comprises suspending an ore infinely divided condition in a liquid carrier to form a pulp, intimatelyintermixing the pulp and a flotation reagent in a zone of classificationunder the combined influence of agitation and aeration to conditionfines in the pulp, separating the conditioned constituents from theother constituents of the pulp by a circulatory movement of the variousconstituents upwardly through one zone and downwardly through asuccessive zone, overflowing substantially all the liquid, fines in thepulp and mineral bearing froth together at the surface of the body,whereby said froth and the uplift of material serve to raise largerparticles to the overflow inducing, settling of the remaining solids ofthe classification, and returning same for regrinding.

20. The method of classifying solids in liquid suspension, whichcomprises agitating a pulp, continuously introducing air into the zoneof agitation, directing the material in a circulatory movement upwardlythrough an inner zone and downwardly through a larger outer zone, underthe combined influence of agitation and aeration, overflowingsubstantially all the liquid, fines and froth together at the'surface,and inducing a settling of coarse material in the pulp by movementthereof through said outer zone beyond the zone of agitation.

21. The methodof classifying solids in liquid suspension which comprisesagitating a pulp, continuously introducing air in the zone of agitation,directing the material in a circulatorymovement upwardly through aninner zone and downwardly through a larger outer zone, under thecombined influence of agitation and aeration, overflowing substantiallyall the liquid, fines and froth together at the surface, inducing asettling of coarse material in the pulp by movement thereof through saidouter zone beyond the zone of agitation, and subjecting the settledmaterial to a de-watering treatment.

22. The method of treating ore which comprises grinding an ore,suspending the ground product in a liquid carrier to form a pulp,feeding the pulp and a flotation reagent having an affinity for one ofthe pulp constituents, into a. zone of primary classification intimatelyintermixing the pulp and reagent under the influence of agitation andaeration in said zone to condition the fines, overflowing substantiallyall the liquid,

fines and froth together from the surface of the body, subjecting thefines separated by the primary classification directly to a frothflotation treatment to reject fine gangue, inducing settling of theremaining solids of the primary classification, through a secondaryclassification, and re turning same for regrinding.

23. The. method of treating ore which comprises grinding an arc,suspending the ground product in a liquid carrier to form a pulp,feeding pulp and a flotation reagent having an affinity for one of thepulp constituents into a zone of primary classification, intimatelyintermixing the pulp and reagent under the influence of agitation andaeration in said zones to condition the fines, overflowing substantiallyall the liquid, fines and froth together fromthe surface of the body,subjecting the fines separated by the primary classification directly toa froth flotation treatment to reject fine gangue, inducing settling ofthe remaining solids of the primary classification, through a secondaryclassification, returning same for regrinding, and returning fines fromthe secondary classification zone to the primary classification zone.

24. The method of classifying finely divided solids in liquid suspensionwhich comprises subjecting a pulp to mechanical agitation,continuouslyintroducing air into the zone of mechanical agitation toform a mineral bearing froth, directing the material upwardly throughone zone under the influence of the agitation, and aeration, dischargingsubstantially all liquid, fines, and formed froth together at thesurface into an overflow, whereby said froth and the uplift of materialserve to raise larger particles to said overflow inducing a settling ofcoarse material in another zone out of the zone of agitation, subjectingthe settled material to a secondary classification in a de-watering zoneand returning fines from the secondary classification to the agitationzone under the pumping influence of the mechanical agitation.

25. The method of classifying finely divided solids in liquid suspensionwhich comprises subjecting the pulp to mechanical agitation,continuously introducing air into the zone of mechanical agitation toform a mineral bearing froth, directing the material upwardly throughone zone under the influence of the agitation, and aeration, dischargingsubstantially all liquid, fines and formed froth together at the surfaceinto an overflow, whereby said froth and the uplift of material serve toraise larger particles to said overflow inducing a settling of coarsematerial in another zone beyound the zone of agitation, and regulatingthe elevating action of the aeration by varying the quantity of air admitted to the mechanical agitation zone.

C. DAMAN.

